In contention-based uplink data transmission, a user equipment (UE) transmits data without dedicated resources. Thus, it is possible that different UEs transmit data on the same resource, resulting in data collision. To make the data transmission reliable, a base station is required to acknowledge data successfully received from different UEs, that is, to send an acknowledgement (ACK) information to corresponding UE. Consequently, it is necessary to explicitly or implicitly indicate which ACK belongs to which UE when the base station transmits ACK information.
An intuitive implicit indication method is establishing a one-to-one mapping relationship table related to ACK information based on user equipment identifiers (UE-IDs) for all UEs registered in a base station. In each time of feedback, the base station broadcasts the above relationship table to all UEs, and the UE may obtain corresponding ACK information by receiving and demodulating the relationship table. A biggest defect of the above UE-ID-based ACK feedback (it may be called as UIAF) method is that when only a few UEs are in an active state, a great part of resources in the above relationship table do not carry valid data.
In IEEE 802.11, a relationship between ACK information and a UE is explicitly expressed; in particular, the ACK information is transmitted by a specific control frame containing corresponding UE-IDs. Generally speaking, a size of a UE-ID is ┌log2 N┐ bits; however, for an ACK information of only one bit, overhead of such a method is still relatively high.
In the 3rd generation partnership project (3GPP) long term evolution (LTE), the above signaling overhead is avoided by the researchers via one-to-one mapping between the ACK information and pre-allocated transmitting resources of the UE. However, unfortunately, the above transmitting resource based ACK feedback (it may be called as REAF) method in the 3GPP LTE cannot be directly used in contention-based data transmission, as in the contention-based data transmission, the resources are not dedicated to the UE.
In summary, there is a currently urgent need for a feedback method for ACK information, which is relatively low in signaling overhead, reliable in performance, and applicable to contention-based data transmission scenarios.
It should be noted that the above description of the background is merely provided for clear and complete explanation of this disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of this disclosure.
Documents advantageous to understanding of this disclosure and conventional technologies are listed below, which are incorporated herein by reference, as they are fully described in this text.    [1] D. L. Donoho, “Compressed sensing,” IEEE Transactions on Information Theory, vol. 52, no. 4, pp. 1289-1306, 2006.    [2] D. Needell and J. A. Tropp, “Cosamp: Iterative signal recovery from incomplete and inaccurate samples,” Applied and Computational Harmonic Analysis, vol. 26, no. 3, pp. 301-321, 2009.    [3] X. Yang, Q. Cui, E. Dutkiewicz, X. Huang, X. Tao and G. Fang, “Anti-noise-folding regularized subspace pursuit recovery algorithm for noisy sparse signals,” Wireless Communications and Networking Conference (WCNC), 2014 IEEE, Istanbul, 2014, pp. 275-280.    [4] V. Chandar, D. Shah and G. W. Wornell, “A simple message-passing algorithm for compressed sensing,” Information Theory Proceedings (ISIT), 2010 IEEE International Symposium on, Austin, Tex., 2010, pp. 1968-1972.